1. Field of the Invention
The present invention relates to a mobile communications terminal, and particularly, to a mobile communications terminal for supporting Space-Time Hybrid Automatic Repeat reQuest (HARQ) schemes, which is capable of implementing high-speed and high-reliable packet data transmissions, and to a method thereof.
2. Discussion of the Background Art
In general, a mobile communications terminal is a communication device capable of providing a wireless call to another party and providing a wireless connection anytime and anywhere by a switching control of an MSC (Mobile Switching Center) while moving in a service region formed by a BS (Base Station). Especially, a mobile communications terminal having a large display device and a camera function for capturing videos (moving pictures) and images is recently gaining popularity.
For the mobile communications terminal, there are various types of mobile communications systems employed, such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Global System for Mobile communications (GSM), and the like. International Telecommunication Union (ITU) has chosen International Mobile Telecommunication 2000 (IMT-2000) as a third generation mobile communications system for supplying multimedia services having a better quality regardless of regions.
At the beginning of the third generation mobile communication market, particularly, an advent of third generation competitive services, such as a wireless RAN, digital multimedia broadcast, portable Internet, and the like, requests High Speed Downlink Packet Access (HSDPA) to be quickly advanced into the market. The HSDPA denotes an access technique which is a method located on an evolution of the existing asynchronous IMT-2000 to thus be additionally employed for a high-speed data transmission over downlink. The HSDPA can advantageously increase a downlink transmission speed and decrease transmission delay accordingly.
Here, advanced mobile communications systems such as WCDMA and CDMA2000 systems use convolutional and turbo codes to support high-speed and high-reliable packet data transmission with a low bit error rate (BER) of less than 10−6. The high-speed and high-reliable packet data transmission has become an important issue in 3.5-generation mobile communications systems such as the HSDPA system employing the turbo code.
Here, the turbo code shows an excellent BER performance at the same signal-to-noise ratio (SNR) region as compared to the convolutional code. However, the turbo code shows a poor error-floor effect at the moderate-to-high SNR and provides a lower gain even with short interleaver sizes.
A Hybrid Automatic Repeat reqQuest (HARQ) where an ARQ technique is combined with channel codes has been used to lower the packet error rate, and is suitable for a high-speed packet data transmission with the different quality of service (QoS) over wireless channels. However, retransmissions with the fixed code rate results in the relatively poor delay of transmission and the waste of bandwidth. The technologies (schemes) cannot support full flexibility in terms of fixed code rates, error protection and multiple antennas.
Furthermore, in the mobile communications terminal for supporting the HARQ technique according to the related art and the method thereof, the HARQ technique employing a rate-compatible punctured serial concatenated convolutional code is used. Accordingly high-speed and high-reliable packet data transmission cannot be efficiently implemented.